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Options and methods for instrumentation of Test Blanket Systems for experiment control and scientific mission
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ARTICLE IN PRESS Fusion Engineering and Design xxx (2014) xxx–xxx
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Options and methods for instrumentation of Test Blanket Systems for experiment control and scientific mission Pattrick Calderoni ∗ , Italo Ricapito, Milan Zmitko, Dobromir Panayotov, Joelle Vallory, Dieter Leichtle, Yves Poitevin Fusion for Energy, Barcelona, Spain
h i g h l i g h t s • This work defined options and methods to instrument ITER TBSs based on functional categories: safety, interlock and control and scientific exploitation based on the ITER research program.
• Presented the general architecture of the HCLL and HCPB Test Blanket System Instrumentation and Control. • Defined safety and interlock sensors count and technology selection based on preliminary safety analysis. • Discussed the development status of scientific instrumentation, with focus on integration with design and fulfillment of TBM research program.
a r t i c l e
i n f o
Article history: Received 16 September 2013 Received in revised form 20 December 2013 Accepted 21 January 2014 Available online xxx Keywords: ITER TBM Fusion blanket Tritium Instrumentation
a b s t r a c t Europe is currently developing two reference breeder blankets concepts for DEMO reactor specifications that will be tested in ITER under the form of Test Blanket Modules (TBMs): the Helium-Cooled Lithium-Lead (HCLL) concept which uses the eutectic Pb-16Li as both breeder and neutron multiplier; the Helium-Cooled Pebble-Bed (HCPB) concept which features lithiated ceramic pebbles as breeder and beryllium pebbles as neutron multiplier. Each TBM is associated with several sub-systems required for their operation; together they form the Test Blanket System (TBS). This paper presents the state of HCLL and HCPB TBS instrumentation design. The discussion is based on the systems functional analysis, from which three main categories of instrumentation are defined: those relevant to safety functions; those relevant to interlock functions; those designed for the control and scientific exploitation of the devices based on the TBM program objectives. © 2014 Elsevier B.V. All rights reserved.
1. Introduction ITER Test Blanket Systems have been the subject of research activity in European Fusion Laboratories for several years, first under the frame of the European Fusion Development Agreement (EFDA), and more recently under the Fusion for Energy (F4E) framework [1,2]. The Helium Cooled Lithium Lead (HCLL) Test Blanket Module (TBM) uses Pb-16Li eutectic (liquid at operating temperatures) both as tritium breeding material and neutron multiplier [3]. The Helium Cooled Pebble Bed (HCPB) TBM uses the Lithium orthosilicate Li4 SiO4 or metatitanate Li2 TiO3 as tritium breeding material and Beryllium as neutron multiplier, both in the form of pebbles [4]. The TBMs are equipped with a radiation shield,
∗ Corresponding author. Tel.: +34 933201185. E-mail addresses: [email protected], [email protected] (P. Calderoni).
forming the TBM sets, both of which are housed in ITER Equatorial port #16 [5]. The TBM sets are then connected to several ancillary sub-systems, with which they form the Test Blanket Systems (TBS). They are essentially forced convection fluid loops, and for the purpose of this paper they can be classified as cooling and tritium systems, according to their main function. The HCLL TBS includes an additional sub-system to circulate the liquid metal breeder [6,7]. Component specific instrumentation will be defined by ongoing design activities and are not addressed in this paper, therefore the sub-systems design details are not essential for the analysis summarized in this work. The HCLL and HCPB TBSs are completely independent from each other at the functional level, only sharing physical space and supporting structures. They will therefore be equipped with separate Instrumentation and Control (I&C) systems, and related sensors and actuators. The two I&C systems have not been designed in detail yet, but preliminary considerations following ITER guidelines [8] have been made in support of the preparation of the
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Please cite this article in press as: P. Calderoni, et al., Options and methods for instrumentation of Test Blanket Systems for experiment control and scientific mission, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.01.054
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Fig. 1. HCLL TBS I&C architecture.
Preliminary Safety Report (PrSR) [9]. The I&C architecture of the HCLL TBS shown in Fig. 1 is the same as the HCPB TBS, and mirrors at the level of Plant the architecture of ITER I&C. Here the four sub-systems of the HCLL TBS are mentioned: the liquid metal loop (PbLi loop), the Helium Cooling System (HCS) and Coolant Purification System (CPS) (referred together as cooling systems in this paper) and the Tritium Extraction System (TES). Acronyms related to the four different TBM modules are described in Section 3.2. The sensors considered in the scheme are the subject of this analysis. Those directly connected to the Plant Safety System (PSS) and Plant Interlock System (PIS) are considered in Section 2, while the others in Section 3. All the results and conclusions presented in this paper are provided as an update of ongoing design activities and shall be considered as preliminary indications until the completion of the ITER Design Review process for the two TBSs, starting with the Conceptual Design Review (CDR) planned for 2014.
2. Safety and interlock instrumentation TBS components contribute in the two fundamental ITER facility safety functions, which are radioactive material confinement and limitation of internal and external exposure to ionizing radiation [10]. In order to fulfill these general requirements three safety functions are identified specifically for the TBS, which are called upon detection of abnormal conditions by safety relevant instrumentation: • the isolation of TBS sub-systems;
• the controlled release of gas in the event of over-pressurization of a sub-system; • the call to the ITER Central Safety System (CSS) for plasma termination. In general, the isolation of the TBS sub-systems is the first safety function foreseen in case abnormal conditions are detected. The combined result of such isolation is to contain the whole TBS inventory of tritium and mobile activated materials within the TBS primary confinement and to place it in its safest state by confining it as much as possible within components housed in Port Cell 16 and away from the interface with other ITER systems. The second safety function is the activation of the pressure suppression system for any loop in which a condition of abnormal over-pressure is detected. The third safety function is the call from the TBS Plant Safety System for the activation of the ITER Fusion Power Shutdown System trough CSS. As part of the definition of the safety functions, trigger events have been identified as well as the sensors that are responsible for its measurement, most of which are deployed in the ancillary subsystems. The only exception is temperature sensors placed on the two TBMs first wall [3]. The sensors connected to the PSS and PIS are similar to those used for conventional control in terms of technology. The implication of the safety functional category is related to the more stringent requirements, because sensors participating in nuclear safety functions will have to be qualified according to ITER rules and applicable nuclear standards. However, at this stage of development the instruments identified in pre-conceptual design activities for sub-systems components also apply to safety
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and interlock sensors and represent the state-of-the-art for TBS application, considering also the emphasis on adopting as much as possible commercially available instrumentation [11]. The ongoing TBS instrumentation development activities at F4E will provide further assessment of the analysis, including experimental testing for operating conditions that are outside of the range of certification offered by commercial vendors, and integration in the system design [12]. The function of safety sensors is to ensure that TBS complies with the ITER requirements toward public and workers protection, while the function of interlock sensor is aimed toward investment protection. They measure: • fluid temperature, by Type K thermocouples and resistance temperature detectors (RTD) in welded thermo-wells; • fluid pressure by capacitive (diaphragm) sensors connected thru welded capillaries (tap lines); • helium bulk flow rate by Coriolis flow meters installed in the cold section of the loops. The only other sensor not included in the categories above considered in the safety function is the current sensor of the cooling system circulator, which is an industrial component and will be designed by the manufacturer according to TBS requirements. In the case of pressure and temperature four locations have been considered for each sub-system operating with the 2 out of 3 logic and one redundant location. Furthermore, the section of the PSS system with the highest safety classification (SIC1) is composed of two duplicate trains (A and B) with independent sensors. As a result the total count of PSS sensors is 60 for the HCLL TBS and 56 for the HCPB TBS. The signals from PSS sensors are duplicated and routed to the PIS (with qualified isolation devices) when the sensors measurement needed is common, therefore the count of PIS sensors represents the additional sensors deployed for interlock functions only. As a result the total count for PIS sensors is 12 for the HCLL TBS and 8 for the HCPB TBS. 3. Conventional control instrumentation Conventional control instrumentation serves two major functions: assuring that the TBS operates in nominal conditions, within the margins defined by design and exploiting the test campaign toward the fulfillment of the TBM program scientific mission. Sensors related to control are mostly deployed in the ancillary systems, and basically extend the function of those described in Section 2. Scientific instrumentation is mainly deployed in the TBMs, with the mission of validating technology and predictive tools for blanket concepts relevant to fusion energy systems. 3.1. TBS sub-systems The I&C architecture foresees independent control at subsystem level for all the remaining instrumentation. The data received will then be integrated at TBS (Plant) level before routing it to the ITER CODAC (Fig. 1). Options for sensors technology and solutions for their deployment have been identified in research activities related to TBS components [11]. However, while for safety and interlock sensor the list presented in Section 2 has been validated by recent activities related to the preparation of the Preliminary Safety Report for the two TBS, for conventional control sensors this consolidation is part of ongoing design activities. In particular, the emphasis on technical consistency and integration at TBS level is expected to reduce the requirements in terms of number of sensors. Based on the current design, the total sensors count for HCLL is 583: 275 deployed in the cooling systems, 92 in
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the tritium systems and 217 in the liquid metal loop. For the HCPB the total sensors count is 437: 275 deployed in the cooling systems and 162 in the tritium systems. In addition to the measurement described in Section 2 (for fluid temperature, pressure and bulk flow rate), but extended to other locations, control sensors will measure: • gas streams chemical composition, including: actively controlled mixtures (for example, helium and hydrogen), impurities and tritium concentration. This is performed in each independent loop by a system in stages connected thru welded sampling lines comprised by a mass spectrometer, an hygrometer and an ion chamber for tritium counting; • mechanical loads, in particular vibration (by accelerometers), as well as forces and stress related to thermal expansion due to phase changes in the liquid metal (by resistive strain gauges), measured in critical components identified by design analysis; • liquid metal surface level (by microwave radar sensor) in all the tanks included in the liquid metal loop. Additional scientific instrumentation is deployed in the ancillary sub-systems to validate components performance and for tritium accountancy and control. Component-specific instrumentation (for example, installed in the liquid metal loop cold trap or in getter beds of the helium purification system) is part of ongoing design activities and is not discussed in this paper. In relation to tritium, accurate accountancy in all the sub-systems involved with tritium transport phenomena is necessary to provide the assessment of the blanket concept in terms of tritium breeding performance [13]. For this purpose, all the tritium containing helium streams are routed to the Tritium Accountancy Station (TAS), which is designed to collect measure and dispose all the tritium generated in the TBM [14]. For accountancy purpose the tritium generated in the HCLL liquid metal breeder is measured in the helium stream at the output of the Tritium Extraction Unit. However, the development of sensors capable of measuring tritium concentration in Pb-16Li remains one of the objectives of the ongoing research activities [15], as they would provide key additional data toward the validation of predictive tools. 3.2. Test Blanket Modules instrumentation The aspect of design integration plays a fundamental role in determining the feasibility of instrumentation deployment in the HCLL and HCPB TBMs. Since design activities in preparation of the Conceptual Design Review are still ongoing, the current state of TBM sensors development is in the research and feasibility validation phase. This is particularly true for the scientific instrumentation to be deployed in the TBMs Breeding Units (BU), since in this phase the focus of the design is the TBM structure (the TBM box and the stiffening grids which define the BU volume). To this regard, the preferred design solution for the key issue of instruments penetration into the TBM back plate is the use of hollow stiffening rods for both HCLL and HCPB TBM. One item for which an integrated technical solution has been developed is the structure temperature measurement, performed again by thermocouples and included as interlock relevant sensors [3]. The TBM scientific instrumentation is primarily deployed to collect data during ITER test campaigns. Four TBMs will be tested in sequence over the first 10 years of ITER operation for each TBS [16]. The instrumentation deployed in each TBM is tailored to the conditions to which it will be exposed and must be designed to fulfill the objective of each test phase. List of technical solutions and related development plans for the sensors required in each phase have been prepared in aforementioned research activities and summarized below. They are the basis of the ongoing TBM instrumentation
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development program at F4E [12]. The objectives listed below are only those that rely primarily on TBM instrumentation for their execution. Items evaluated thru Post Irradiation Examination (PIE), periodic samplings in sub-system components or that relate to the integrated performance of TBS are not included. Sensors installed on the Electro Magnetic (EM) TBMs are used primarily to: a. b. c. d. e.
test the effect of electromagnetic loads on the TBM set; validate the integrity of the TBM set structure; validate the operation of the TBS sub-system; test heat extraction from the TBM first wall; for the HCLL TBM, test the effect of MHD phenomena.
Since the EM-TBM will not be exposed to neutrons (and the related volumetric heat loads), the requirements for instrumentation are less stringent than the subsequent phases in terms of radiation effects and temperature. Items (a) and (b) are accomplished primarily by measuring magnetic field and induced currents by magnetic sensors, and monitoring forces, strain, displacements and vibrations by optical fiber sensors. Among magnetic sensors, Hall-effect sensors, and induction-coils sensors (in particular pickup coils and Rogowski coils) are considered based on their simple operating principles, possibility of miniaturization, simple implementation, and good applicability for current sensing. Fiber optics are considered due to their intrinsic advantages, like resistance to electromagnetic interference, non-electrical conductivity, passive measurements, small size and low weight, and the option of multipoint measurements. Item (c) is accomplished by measuring fluids temperature and pressure within the TBM structure with the same sensors adopted for the sub-systems. The fiber optic sensors discussed above will be used to measure temperature in additional locations. Item (d) is accomplished by measuring the first wall temperature by means of thermocouples embedded in the TBM structure. Additional information is provided by the ITER optical thermometer (VIS-IR camera) that monitors the plasma exposed surfaces of the in-vessel components. Some limited information related to item (e) is derived from the general performance of the liquid metal loop, for example the total pressure drop in the TBM. The development of miniaturized probes that can simultaneously measure temperature and electric potential in contact with liquid metal is foreseen as part of ongoing F4E activities. Their deployment in one or more HCLL BU would allow mapping of the electric potential to validate predictive models during operation in the ITER electromagnetic field. Sensors installed in the Thermal-Neutronic (TN) TBM are used primarily to: f. test the performance of neutronics sensors; g. provide a preliminary assessment of the TBM neutronic response (neutron flux, energy distribution, wall load; tritium production rate). The TN-TBM will be exposed to low energy neutrons from DD plasma and short, low density pulses of neutrons in the fusion relevant spectrum from the first period of the D-T low-duty cycle phases. The main objective in terms of neutronics response is therefore the validation of sensors performance in the ITER environment (items (f) and (g)). The lower temperature of HCPB BUs (due to lower volumetric heating in the breeding pebble beds) can be exploited to deploy temperature-limited sensors specific to TN-TBM, in particular for the measurement of the tritium production rate. The development of neutronics sensors is the subject of specific F4E research activities. Four types of sensors are considered: neutron activation foils system (NAS), self-powered neutron detectors (SPND), single crystal diamond detectors (SCD)
and miniaturized fission chambers (MFC). The deployment of all or some sensor type depends on the validation of their capability to operate efficiently at TBM conditions and the feasibility of design integration, in particular for the NAS, which involves the periodic transfer of activated foils from the Port Cell to the TBM thru a pneumatic transfer line. If feasible, the NAS should be the primary focus for the TN-TBM given its flexibility to differentiate among neutrons energy and tailor its measurement efficiency to the expected fluence. Further details and updates are provided in a companion contribution to this conference [17]. Sensors installed in the Neutronic-Tritium/ThermoMechanic (NT/TM) TBM are used primarily to: h. test TBM neutronic response (neutron flux, energy distribution, wall load; tritium production rate); i. provide a preliminary assessment of the TBM thermo-mechanical behavior, in particular in transient mode. The NT/TM-TBM will be exposed to short pulses of neutrons with fusion relevant spectrum during the last period of the D-T low-duty cycle and first period of the D-T high-duty cycle phases. Item (h) is accomplished by the same sensors described for item (g), although the priority now should be given to on-line sensors with efficient dynamic response. Item (i) is accomplished by the same sensors described for item (b), providing that the ongoing development activities can demonstrate that the fiber optics employed in the EM-TBM can withstand the low level of radiation damages expected. In addition, dedicated sensors are under development to measure the thermo-mechanical response of the HCPB pebble beds, based on the use of thermocouples for temperature, linear variable differential transformer (LVDT) for displacement and piezoelectric sensors for contact pressure. Sensors installed in the Integral (INT) TBM are used primarily to: j. test the TBM thermo-mechanical behavior; k. test TBM heat extraction; l. validate fabrication technologies, in particular for joints, and manufacturing processes under thermal cycling and low-level irradiation. The INT TBM is exposed to the ITER reference pulses of fusion relevant neutrons during the last period of the high duty cycle D-T phase. Its objective is to extend the reliability and operational performance database for the tested TBS in a DT fusion device under operating conditions relevant to a fusion energy system (except for neutron fluence) and for an extended period of time. Since the longterm integrated response is the main focus, in particular toward the assessment of tritium self-sufficiency for the tested blanket concepts, the sensors deployed in the INT-TBM should maximize reliability and minimize intrusiveness. All items are accomplished by sensors described in relation to items (d) and (i). The use of a limited number of thermocouples for temperature measurement inside the TBM is considered as alternative, pending the assessment of the stability of the fiber optic sensors developed for the TBM under irradiation. Neutronic sensors are installed to quantify the source term for the assessment of thermo-mechanical behavior and tritium cycle efficiency. While the use of NAS is excluded due to its intrusiveness, all other sensors related to item (f), (g) and (h) are considered, pending results of performance validation and design integration studies. 4. Conclusions This paper identifies options and methods to instrument ITER Test Blanket Modules based on three functional categories: sensors
Please cite this article in press as: P. Calderoni, et al., Options and methods for instrumentation of Test Blanket Systems for experiment control and scientific mission, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.01.054
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relevant to safety, interlock, and sensors designed for the control and scientific exploitation of the devices based on the ITER research program. Although the proposed instrumentation refers specifically to the HCLL and HCPB TBS, elements of the methodology and selection analysis are relevant to all TBMs to be tested in ITER. Acknowledgements This work was carried out within the framework of Fusion for Energy. The views and opinions expressed herein do not necessarily reflect those of the European Commission. References [1] Y. Poitevin, L.V. Boccaccini, M. Zmitko, I. Ricapito, J.-F. Salavy, E. Diegele, et al., Fusion Eng. Des. 85 (2010) 2340–2347. [2] L.M. Giancarli, M. Abdou, D.J. Campbell, V.A. Chuyanov, M.Y. Ahn, M. Enoeda, et al., Fusion Eng. Des. 87 (2012) 395–402. [3] G. Aiello, G. de Dinechin, L. Forest, F. Gabriel, A. Li Puma, G. Rampal, et al., Fusion Eng. Des. 86 (2011) 2129–2134. [4] F. Cismondi, S. Kecskes, M. Ilic, G. Legradi, B. Kiss, O. Bitz, et al., Fusion Eng. Des. 84 (2009) 607–612.
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[5] L.V. Boccaccini, A. Aiello, O. Bede, F. Cismondi, L. Kosek, T. Ilkei, et al., Fusion Eng. Des. 86 (2011) 478–483. [6] I. Ricapito, O. Bede, L.V. Boccaccini, A. Ciampichetti, B. Ghidersa, L. Guerrini, et al., Fusion Eng. Des. 85 (2010) 1154–1161. [7] A. Aiello, A. Ciampichetti, F. Cismondi, B.E. Ghidersa, T. Ilkei, L. Kosek, et al., Fusion Eng. Des. 86 (2011) 602–606. [8] A. Wallander, L. Abadie, H. Dave, F. Di Maio, H.K. Gulati, C. Hansalia, et al., Fusion Eng. Des. 85 (2010) 529–534. [9] Y. Poitevin, I. Ricapito, M. Zmitko, D. Panayotov, P. Calderoni, J. Galabert, et al., European ITER Test Blanket Module Systems: Progresses and Challenges towards Licensing, 2014. [10] D. Panayotov, Y. Poitevin, L. Guerrini, M. Zmitko, L. Giancarli, M. Iseli, et al., Fusion Eng. Des. 87 (2012) 1035–1039. [11] A. Li Puma, G. Aiello, F. Gabriel, G. Laffont, G. Rampal, J.-F. Salavy, Fusion Eng. Des. 85 (2010) 1642–1652. [12] P. Calderoni, I. Ricapito, Y. Poitevin, Fusion Eng. Des. 88 (2013) 2440–2443. [13] I. Ricapito, P. Calderoni, Y. Poitevin, A. Aiello, Fusion Eng. Des. (2014). [14] D. Demange, C.G. Alecu, N. Bekris, O. Borisevich, B. Bornschein, S. Fischer, et al., Fusion Eng. Des. 87 (2012) 1206–1213. [15] A. Ciampichetti, M. Zucchetti, I. Ricapito, M. Utili, A. Aiello, G. Benamati, J. Nucl. Mater. 367–370 (2007) 1090–1095. [16] V.A. Chuyanov, D.J. Campbell, L.M. Giancarli, Fusion Eng. Des. 85 (2010) 2005–2011. [17] D. Leichtle, M. Angelone, P. Batistoni, P. Calderoni, U. Fischer, J. Izquierdo, et al., The F4E Programme on Nuclear Data Validation and Nuclear Instrumentation Techniques for TBM in ITER, 2014.
Please cite this article in press as: P. Calderoni, et al., Options and methods for instrumentation of Test Blanket Systems for experiment control and scientific mission, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.01.054
ARTICLE IN PRESS Fusion Engineering and Design xxx (2014) xxx–xxx
Contents lists available at ScienceDirect
Fusion Engineering and Design journal homepage: www.elsevier.com/locate/fusengdes
Options and methods for instrumentation of Test Blanket Systems for experiment control and scientific mission Pattrick Calderoni ∗ , Italo Ricapito, Milan Zmitko, Dobromir Panayotov, Joelle Vallory, Dieter Leichtle, Yves Poitevin Fusion for Energy, Barcelona, Spain
h i g h l i g h t s • This work defined options and methods to instrument ITER TBSs based on functional categories: safety, interlock and control and scientific exploitation based on the ITER research program.
• Presented the general architecture of the HCLL and HCPB Test Blanket System Instrumentation and Control. • Defined safety and interlock sensors count and technology selection based on preliminary safety analysis. • Discussed the development status of scientific instrumentation, with focus on integration with design and fulfillment of TBM research program.
a r t i c l e
i n f o
Article history: Received 16 September 2013 Received in revised form 20 December 2013 Accepted 21 January 2014 Available online xxx Keywords: ITER TBM Fusion blanket Tritium Instrumentation
a b s t r a c t Europe is currently developing two reference breeder blankets concepts for DEMO reactor specifications that will be tested in ITER under the form of Test Blanket Modules (TBMs): the Helium-Cooled Lithium-Lead (HCLL) concept which uses the eutectic Pb-16Li as both breeder and neutron multiplier; the Helium-Cooled Pebble-Bed (HCPB) concept which features lithiated ceramic pebbles as breeder and beryllium pebbles as neutron multiplier. Each TBM is associated with several sub-systems required for their operation; together they form the Test Blanket System (TBS). This paper presents the state of HCLL and HCPB TBS instrumentation design. The discussion is based on the systems functional analysis, from which three main categories of instrumentation are defined: those relevant to safety functions; those relevant to interlock functions; those designed for the control and scientific exploitation of the devices based on the TBM program objectives. © 2014 Elsevier B.V. All rights reserved.
1. Introduction ITER Test Blanket Systems have been the subject of research activity in European Fusion Laboratories for several years, first under the frame of the European Fusion Development Agreement (EFDA), and more recently under the Fusion for Energy (F4E) framework [1,2]. The Helium Cooled Lithium Lead (HCLL) Test Blanket Module (TBM) uses Pb-16Li eutectic (liquid at operating temperatures) both as tritium breeding material and neutron multiplier [3]. The Helium Cooled Pebble Bed (HCPB) TBM uses the Lithium orthosilicate Li4 SiO4 or metatitanate Li2 TiO3 as tritium breeding material and Beryllium as neutron multiplier, both in the form of pebbles [4]. The TBMs are equipped with a radiation shield,
∗ Corresponding author. Tel.: +34 933201185. E-mail addresses: [email protected], [email protected] (P. Calderoni).
forming the TBM sets, both of which are housed in ITER Equatorial port #16 [5]. The TBM sets are then connected to several ancillary sub-systems, with which they form the Test Blanket Systems (TBS). They are essentially forced convection fluid loops, and for the purpose of this paper they can be classified as cooling and tritium systems, according to their main function. The HCLL TBS includes an additional sub-system to circulate the liquid metal breeder [6,7]. Component specific instrumentation will be defined by ongoing design activities and are not addressed in this paper, therefore the sub-systems design details are not essential for the analysis summarized in this work. The HCLL and HCPB TBSs are completely independent from each other at the functional level, only sharing physical space and supporting structures. They will therefore be equipped with separate Instrumentation and Control (I&C) systems, and related sensors and actuators. The two I&C systems have not been designed in detail yet, but preliminary considerations following ITER guidelines [8] have been made in support of the preparation of the
0920-3796/$ – see front matter © 2014 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.fusengdes.2014.01.054
Please cite this article in press as: P. Calderoni, et al., Options and methods for instrumentation of Test Blanket Systems for experiment control and scientific mission, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.01.054
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Fig. 1. HCLL TBS I&C architecture.
Preliminary Safety Report (PrSR) [9]. The I&C architecture of the HCLL TBS shown in Fig. 1 is the same as the HCPB TBS, and mirrors at the level of Plant the architecture of ITER I&C. Here the four sub-systems of the HCLL TBS are mentioned: the liquid metal loop (PbLi loop), the Helium Cooling System (HCS) and Coolant Purification System (CPS) (referred together as cooling systems in this paper) and the Tritium Extraction System (TES). Acronyms related to the four different TBM modules are described in Section 3.2. The sensors considered in the scheme are the subject of this analysis. Those directly connected to the Plant Safety System (PSS) and Plant Interlock System (PIS) are considered in Section 2, while the others in Section 3. All the results and conclusions presented in this paper are provided as an update of ongoing design activities and shall be considered as preliminary indications until the completion of the ITER Design Review process for the two TBSs, starting with the Conceptual Design Review (CDR) planned for 2014.
2. Safety and interlock instrumentation TBS components contribute in the two fundamental ITER facility safety functions, which are radioactive material confinement and limitation of internal and external exposure to ionizing radiation [10]. In order to fulfill these general requirements three safety functions are identified specifically for the TBS, which are called upon detection of abnormal conditions by safety relevant instrumentation: • the isolation of TBS sub-systems;
• the controlled release of gas in the event of over-pressurization of a sub-system; • the call to the ITER Central Safety System (CSS) for plasma termination. In general, the isolation of the TBS sub-systems is the first safety function foreseen in case abnormal conditions are detected. The combined result of such isolation is to contain the whole TBS inventory of tritium and mobile activated materials within the TBS primary confinement and to place it in its safest state by confining it as much as possible within components housed in Port Cell 16 and away from the interface with other ITER systems. The second safety function is the activation of the pressure suppression system for any loop in which a condition of abnormal over-pressure is detected. The third safety function is the call from the TBS Plant Safety System for the activation of the ITER Fusion Power Shutdown System trough CSS. As part of the definition of the safety functions, trigger events have been identified as well as the sensors that are responsible for its measurement, most of which are deployed in the ancillary subsystems. The only exception is temperature sensors placed on the two TBMs first wall [3]. The sensors connected to the PSS and PIS are similar to those used for conventional control in terms of technology. The implication of the safety functional category is related to the more stringent requirements, because sensors participating in nuclear safety functions will have to be qualified according to ITER rules and applicable nuclear standards. However, at this stage of development the instruments identified in pre-conceptual design activities for sub-systems components also apply to safety
Please cite this article in press as: P. Calderoni, et al., Options and methods for instrumentation of Test Blanket Systems for experiment control and scientific mission, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.01.054
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and interlock sensors and represent the state-of-the-art for TBS application, considering also the emphasis on adopting as much as possible commercially available instrumentation [11]. The ongoing TBS instrumentation development activities at F4E will provide further assessment of the analysis, including experimental testing for operating conditions that are outside of the range of certification offered by commercial vendors, and integration in the system design [12]. The function of safety sensors is to ensure that TBS complies with the ITER requirements toward public and workers protection, while the function of interlock sensor is aimed toward investment protection. They measure: • fluid temperature, by Type K thermocouples and resistance temperature detectors (RTD) in welded thermo-wells; • fluid pressure by capacitive (diaphragm) sensors connected thru welded capillaries (tap lines); • helium bulk flow rate by Coriolis flow meters installed in the cold section of the loops. The only other sensor not included in the categories above considered in the safety function is the current sensor of the cooling system circulator, which is an industrial component and will be designed by the manufacturer according to TBS requirements. In the case of pressure and temperature four locations have been considered for each sub-system operating with the 2 out of 3 logic and one redundant location. Furthermore, the section of the PSS system with the highest safety classification (SIC1) is composed of two duplicate trains (A and B) with independent sensors. As a result the total count of PSS sensors is 60 for the HCLL TBS and 56 for the HCPB TBS. The signals from PSS sensors are duplicated and routed to the PIS (with qualified isolation devices) when the sensors measurement needed is common, therefore the count of PIS sensors represents the additional sensors deployed for interlock functions only. As a result the total count for PIS sensors is 12 for the HCLL TBS and 8 for the HCPB TBS. 3. Conventional control instrumentation Conventional control instrumentation serves two major functions: assuring that the TBS operates in nominal conditions, within the margins defined by design and exploiting the test campaign toward the fulfillment of the TBM program scientific mission. Sensors related to control are mostly deployed in the ancillary systems, and basically extend the function of those described in Section 2. Scientific instrumentation is mainly deployed in the TBMs, with the mission of validating technology and predictive tools for blanket concepts relevant to fusion energy systems. 3.1. TBS sub-systems The I&C architecture foresees independent control at subsystem level for all the remaining instrumentation. The data received will then be integrated at TBS (Plant) level before routing it to the ITER CODAC (Fig. 1). Options for sensors technology and solutions for their deployment have been identified in research activities related to TBS components [11]. However, while for safety and interlock sensor the list presented in Section 2 has been validated by recent activities related to the preparation of the Preliminary Safety Report for the two TBS, for conventional control sensors this consolidation is part of ongoing design activities. In particular, the emphasis on technical consistency and integration at TBS level is expected to reduce the requirements in terms of number of sensors. Based on the current design, the total sensors count for HCLL is 583: 275 deployed in the cooling systems, 92 in
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the tritium systems and 217 in the liquid metal loop. For the HCPB the total sensors count is 437: 275 deployed in the cooling systems and 162 in the tritium systems. In addition to the measurement described in Section 2 (for fluid temperature, pressure and bulk flow rate), but extended to other locations, control sensors will measure: • gas streams chemical composition, including: actively controlled mixtures (for example, helium and hydrogen), impurities and tritium concentration. This is performed in each independent loop by a system in stages connected thru welded sampling lines comprised by a mass spectrometer, an hygrometer and an ion chamber for tritium counting; • mechanical loads, in particular vibration (by accelerometers), as well as forces and stress related to thermal expansion due to phase changes in the liquid metal (by resistive strain gauges), measured in critical components identified by design analysis; • liquid metal surface level (by microwave radar sensor) in all the tanks included in the liquid metal loop. Additional scientific instrumentation is deployed in the ancillary sub-systems to validate components performance and for tritium accountancy and control. Component-specific instrumentation (for example, installed in the liquid metal loop cold trap or in getter beds of the helium purification system) is part of ongoing design activities and is not discussed in this paper. In relation to tritium, accurate accountancy in all the sub-systems involved with tritium transport phenomena is necessary to provide the assessment of the blanket concept in terms of tritium breeding performance [13]. For this purpose, all the tritium containing helium streams are routed to the Tritium Accountancy Station (TAS), which is designed to collect measure and dispose all the tritium generated in the TBM [14]. For accountancy purpose the tritium generated in the HCLL liquid metal breeder is measured in the helium stream at the output of the Tritium Extraction Unit. However, the development of sensors capable of measuring tritium concentration in Pb-16Li remains one of the objectives of the ongoing research activities [15], as they would provide key additional data toward the validation of predictive tools. 3.2. Test Blanket Modules instrumentation The aspect of design integration plays a fundamental role in determining the feasibility of instrumentation deployment in the HCLL and HCPB TBMs. Since design activities in preparation of the Conceptual Design Review are still ongoing, the current state of TBM sensors development is in the research and feasibility validation phase. This is particularly true for the scientific instrumentation to be deployed in the TBMs Breeding Units (BU), since in this phase the focus of the design is the TBM structure (the TBM box and the stiffening grids which define the BU volume). To this regard, the preferred design solution for the key issue of instruments penetration into the TBM back plate is the use of hollow stiffening rods for both HCLL and HCPB TBM. One item for which an integrated technical solution has been developed is the structure temperature measurement, performed again by thermocouples and included as interlock relevant sensors [3]. The TBM scientific instrumentation is primarily deployed to collect data during ITER test campaigns. Four TBMs will be tested in sequence over the first 10 years of ITER operation for each TBS [16]. The instrumentation deployed in each TBM is tailored to the conditions to which it will be exposed and must be designed to fulfill the objective of each test phase. List of technical solutions and related development plans for the sensors required in each phase have been prepared in aforementioned research activities and summarized below. They are the basis of the ongoing TBM instrumentation
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development program at F4E [12]. The objectives listed below are only those that rely primarily on TBM instrumentation for their execution. Items evaluated thru Post Irradiation Examination (PIE), periodic samplings in sub-system components or that relate to the integrated performance of TBS are not included. Sensors installed on the Electro Magnetic (EM) TBMs are used primarily to: a. b. c. d. e.
test the effect of electromagnetic loads on the TBM set; validate the integrity of the TBM set structure; validate the operation of the TBS sub-system; test heat extraction from the TBM first wall; for the HCLL TBM, test the effect of MHD phenomena.
Since the EM-TBM will not be exposed to neutrons (and the related volumetric heat loads), the requirements for instrumentation are less stringent than the subsequent phases in terms of radiation effects and temperature. Items (a) and (b) are accomplished primarily by measuring magnetic field and induced currents by magnetic sensors, and monitoring forces, strain, displacements and vibrations by optical fiber sensors. Among magnetic sensors, Hall-effect sensors, and induction-coils sensors (in particular pickup coils and Rogowski coils) are considered based on their simple operating principles, possibility of miniaturization, simple implementation, and good applicability for current sensing. Fiber optics are considered due to their intrinsic advantages, like resistance to electromagnetic interference, non-electrical conductivity, passive measurements, small size and low weight, and the option of multipoint measurements. Item (c) is accomplished by measuring fluids temperature and pressure within the TBM structure with the same sensors adopted for the sub-systems. The fiber optic sensors discussed above will be used to measure temperature in additional locations. Item (d) is accomplished by measuring the first wall temperature by means of thermocouples embedded in the TBM structure. Additional information is provided by the ITER optical thermometer (VIS-IR camera) that monitors the plasma exposed surfaces of the in-vessel components. Some limited information related to item (e) is derived from the general performance of the liquid metal loop, for example the total pressure drop in the TBM. The development of miniaturized probes that can simultaneously measure temperature and electric potential in contact with liquid metal is foreseen as part of ongoing F4E activities. Their deployment in one or more HCLL BU would allow mapping of the electric potential to validate predictive models during operation in the ITER electromagnetic field. Sensors installed in the Thermal-Neutronic (TN) TBM are used primarily to: f. test the performance of neutronics sensors; g. provide a preliminary assessment of the TBM neutronic response (neutron flux, energy distribution, wall load; tritium production rate). The TN-TBM will be exposed to low energy neutrons from DD plasma and short, low density pulses of neutrons in the fusion relevant spectrum from the first period of the D-T low-duty cycle phases. The main objective in terms of neutronics response is therefore the validation of sensors performance in the ITER environment (items (f) and (g)). The lower temperature of HCPB BUs (due to lower volumetric heating in the breeding pebble beds) can be exploited to deploy temperature-limited sensors specific to TN-TBM, in particular for the measurement of the tritium production rate. The development of neutronics sensors is the subject of specific F4E research activities. Four types of sensors are considered: neutron activation foils system (NAS), self-powered neutron detectors (SPND), single crystal diamond detectors (SCD)
and miniaturized fission chambers (MFC). The deployment of all or some sensor type depends on the validation of their capability to operate efficiently at TBM conditions and the feasibility of design integration, in particular for the NAS, which involves the periodic transfer of activated foils from the Port Cell to the TBM thru a pneumatic transfer line. If feasible, the NAS should be the primary focus for the TN-TBM given its flexibility to differentiate among neutrons energy and tailor its measurement efficiency to the expected fluence. Further details and updates are provided in a companion contribution to this conference [17]. Sensors installed in the Neutronic-Tritium/ThermoMechanic (NT/TM) TBM are used primarily to: h. test TBM neutronic response (neutron flux, energy distribution, wall load; tritium production rate); i. provide a preliminary assessment of the TBM thermo-mechanical behavior, in particular in transient mode. The NT/TM-TBM will be exposed to short pulses of neutrons with fusion relevant spectrum during the last period of the D-T low-duty cycle and first period of the D-T high-duty cycle phases. Item (h) is accomplished by the same sensors described for item (g), although the priority now should be given to on-line sensors with efficient dynamic response. Item (i) is accomplished by the same sensors described for item (b), providing that the ongoing development activities can demonstrate that the fiber optics employed in the EM-TBM can withstand the low level of radiation damages expected. In addition, dedicated sensors are under development to measure the thermo-mechanical response of the HCPB pebble beds, based on the use of thermocouples for temperature, linear variable differential transformer (LVDT) for displacement and piezoelectric sensors for contact pressure. Sensors installed in the Integral (INT) TBM are used primarily to: j. test the TBM thermo-mechanical behavior; k. test TBM heat extraction; l. validate fabrication technologies, in particular for joints, and manufacturing processes under thermal cycling and low-level irradiation. The INT TBM is exposed to the ITER reference pulses of fusion relevant neutrons during the last period of the high duty cycle D-T phase. Its objective is to extend the reliability and operational performance database for the tested TBS in a DT fusion device under operating conditions relevant to a fusion energy system (except for neutron fluence) and for an extended period of time. Since the longterm integrated response is the main focus, in particular toward the assessment of tritium self-sufficiency for the tested blanket concepts, the sensors deployed in the INT-TBM should maximize reliability and minimize intrusiveness. All items are accomplished by sensors described in relation to items (d) and (i). The use of a limited number of thermocouples for temperature measurement inside the TBM is considered as alternative, pending the assessment of the stability of the fiber optic sensors developed for the TBM under irradiation. Neutronic sensors are installed to quantify the source term for the assessment of thermo-mechanical behavior and tritium cycle efficiency. While the use of NAS is excluded due to its intrusiveness, all other sensors related to item (f), (g) and (h) are considered, pending results of performance validation and design integration studies. 4. Conclusions This paper identifies options and methods to instrument ITER Test Blanket Modules based on three functional categories: sensors
Please cite this article in press as: P. Calderoni, et al., Options and methods for instrumentation of Test Blanket Systems for experiment control and scientific mission, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.01.054
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relevant to safety, interlock, and sensors designed for the control and scientific exploitation of the devices based on the ITER research program. Although the proposed instrumentation refers specifically to the HCLL and HCPB TBS, elements of the methodology and selection analysis are relevant to all TBMs to be tested in ITER. Acknowledgements This work was carried out within the framework of Fusion for Energy. The views and opinions expressed herein do not necessarily reflect those of the European Commission. References [1] Y. Poitevin, L.V. Boccaccini, M. Zmitko, I. Ricapito, J.-F. Salavy, E. Diegele, et al., Fusion Eng. Des. 85 (2010) 2340–2347. [2] L.M. Giancarli, M. Abdou, D.J. Campbell, V.A. Chuyanov, M.Y. Ahn, M. Enoeda, et al., Fusion Eng. Des. 87 (2012) 395–402. [3] G. Aiello, G. de Dinechin, L. Forest, F. Gabriel, A. Li Puma, G. Rampal, et al., Fusion Eng. Des. 86 (2011) 2129–2134. [4] F. Cismondi, S. Kecskes, M. Ilic, G. Legradi, B. Kiss, O. Bitz, et al., Fusion Eng. Des. 84 (2009) 607–612.
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Please cite this article in press as: P. Calderoni, et al., Options and methods for instrumentation of Test Blanket Systems for experiment control and scientific mission, Fusion Eng. Des. (2014), http://dx.doi.org/10.1016/j.fusengdes.2014.01.054